1. Field of the Invention
This invention relates to an actuator system for providing force feedback to a portable master support as a function of manipulation of an interactive system.
2. Description of Related Art
Present telemanipulation techniques include the use of mechanical masters, open-loop servomasters, and to a lesser extent, closed-loop servomasters. Direct mechanical telemanipulation is often the simplest method, but cannot be used in applications where the slave is not in the immediate vicinity of the master. Closed-loop telemanipulation eliminates the proximity requirement but may necessitate the need to have two nearly identical devices to act as master and slave. This duplication of resources is often prohibitive in terms of cost and payload weight.
Efforts have been made to eliminate the duplicate master by replacing it with force feedback joysticks, sensorized spheres, pistol grips and the like. Although such devices have served their purposes, they have not proved entirely satisfactory under all conditions of service because these devices are less "natural" to an operator since direct similitude does not exist between human hand and robot finger motions. Examples of manual controllers using levers, grippers, handles and the like, with some having force feedback, may be found in the following U.S. Pat. Nos.: 4,795,296; 3,995,831; 4,604,016; 3,618,786; 3,637,092 and 3,771,037.
Those concerned with the development of telemanipulation devices have recognized the disadvantages of such prior art controllers and the need for a dextrous master controller that uses an operator's hand to replace the classical manipulation arm, the conventional keypad contact, the joystick or handle, or other similar structure. Use of the human hand is a natural form of control and is applicable for use with both non-dextrous and dextrous slave devices. Further, because the human hand is used as master, duplication of most hardware is not required and weight, inertia and friction can be reduced. Under most conditions, significant improvements in the time necessary to complete a task can be realized when using the human hand as the master. For example, it has been estimated that an improvement on the order of 10 can be expected on time efficiency when a dextrous master is used in place of a conventional keypad control.
While open-loop dextrous masters create more natural control environments, they lack the ability to bring force feedback to the operator's hand, which in turn limits the utility of the slave device. However, a dextrous master with force feedback, using much of the human hand as master in a closed-loop teleoperations environment, will allow the efficient execution of complex tasks such as assembly and repair involving the telemanipulation of small, intricately-shaped parts. Examples of robotic masters with force feedback and wherein much of the human hand is used as the master may be found in the following U.S. Pat. Nos.: 3,449,008; 3,171,549 and 4,302,138.
U.S. Pat. Nos. 3,414,137 entitled REMOTE HANDLING DEVICE issued Dec. 3, 1968 to Marcel Fortin is typical of telemanipulation devices that employ a squeezable, manipulatable device for remote control. A hand grabbable grip is squeezed causing the remote flexing of a pair of robotic fingers around an object. This device is especially adapted for use in nuclear reactors or dangerous environments.
U.S. Pat. No. 4,302,138 entitled REMOTE HANDLING OF DEVICES issued on Nov. 24, 1981 to Alain Zarudiansky, describes a device for improving the grip and remote handling of an object. An artificial hand, or slave hand, is remotely controlled by the hand of an operator. Sensors on the artificial hand provide for the sensing of tactile parameters. The signals produced by the sensors are applied to actuators located on the backside of the master hand. The master hand may be in the form of a modified glove in which the hand of the operator is inserted. The actuators mounted on the backside glove supply tactile sensations to the hand of the operator. Thus the operator apparently "feels" the object as if the object were being handled directly by the operator. This particular device is especially useful for the handling of objects in dangerous environments, such as in the nuclear or chemical industries, or possibly may be used by an operator in outer space or underwater. The major drawback of such a device is that it is fairly bulky because it requires the sensing and manipulation of the hand from the backside. The hand thus loses a lot of its "feel" because the "feel" of a hand is from the palm not the outside. Thus, the device such as set forth in U.S. Pat. No. 4,302,138 is significantly larger and less effective than the device set forth in the present disclosure.
The foregoing examples demonstrate various prior art attempts to obtain a controller that is more "natural" to the operator. There has been long recognized a need for "natural" dextrous masters that more closely simulate the motions of the finger of a dextrous slave. Unfortunately, no practical system has yet been devised for doing so. Ideally, such a system would have the capability of being hand-holdable in an actual position in the operator's hand. It would also be operable by the operator using natural motions and would be relatively lightweight. A force feedback mechanism would be provided back to the operator's hand in a manner that corresponds directly to the forces generated on the slave. Moreover, the device should be compact, portable, simple in construction and dependable in operation, and safe for the operator.
In an attempt to solve the foregoing challenges, one of the inventors discovered a technique and mechanism set forth in U.S. application Ser. No. 07/396,476 now U.S. Pat. No. 5,004,391 and entitled PORTABLE DEXTROUS FORCE FEEDBACK MASTER FOR ROBOT TELEMANIPULATIONS, the entire contents of which is incorporated by reference into this disclosure. The actuator device described therein includes a compact, hand-held unit that fits within the space defined by the user's palm and fingers and functions as a position controller for a robot having a slave hand. A finger position sensor including a linear, variable differential transformer provides an output signal that is proportional to the distance between the user's fingers. A force feedback system, including a pneumatic micro-actuator, senses the forces exerted by the end effectors of the robot hand and causes a corresponding force to be exerted on the fingers of the user. The foregoing invention was intended primarily for use between the thumb and middle finger of the operator's hand. As such, it limited the ability to provide force feedback between any other fingers of the hand and also required the usage of a special sensor system using a linear differential transformer between the two manipulating digits. However, there now exists on the market sensor-type gloves such as the DataGlove.TM. Model 2 available from VPL Research, Inc., 950 Tower Lane, 14th Floor, Foster City, Calif. 94404 which senses the position of the fingers and provides information with regard to position and orientation to a host computer for a variety of different purposes. A Polhemus-type sensor mounted on the backside of the glove, provides information with regard to the motion of the wrist in space. Sensor gloves such as the DataGlove.TM. typically include fiber optic sensors that are located on the back, i.e. topside, of the glove such that the movement of the fingers is sensed by the fiber optic sensors and transmitted through a fiber optic umbilical bundle back to a glove interface. The glove interface suitable for use with a standard host computer is also available from VPL Research, Inc.
The concept of employing a sensor-type glove in the context of a force feedback system was described in a paper presented at the "Symposium on Dynamics and Control of Biomechanical Systems" December 1989 at the ASME winter annual meeting by the primary inventor.
U.S. Pat. No. 3,171,549 entitled "MECHANICAL HANDLING APPARATUS" issued Mar. 2, 1965 to G. Orloff was cited during prosecution of the patent application Ser. No. 07/661,515. An apparatus includes a pistol grip and finger grips. Hydraulic bellows actuators provides "feel feedback" to the finger grips. This device has the disadvantage of being bulky and less effective than the device set forth in the present invention.